The present invention relates to a circuit substrate suitably incorporated in a battery pack and the like in a laptop personal computer, a mobile phone and so on. The present invention also relates to a battery pack incorporating such a circuit substrate. Further, the present invention relates to a method of manufacturing such a circuit substrate.
For a laptop personal computer for example, a battery pack is available which utilizes a lithium ion battery, or a manganese battery for example. Such a battery pack is detachable from the personal computer itself.
As shown in FIG. 29, a common battery pack P comprises a case 1 and a plurality of batteries 2 encased therein. The case 1 incorporates a circuit substrate 10 including a printed circuit mounted with a connector C and other electronic parts (not illustrated). The circuit substrate 10 serves for battery power supply and electric signal exchange between the batteries 2 and external components. The battery pack P is under a certain limitation in terms of the size of case 1, making it difficult to provide a large internal space other than for the batteries 2. For this reason, the circuit substrate 10 is incorporated as a first and a second substrate splits 11, 12. With this arrangement, the first and the second substrate splits 11, 12 are joined with each other by a joint structure to be described hereafter, and bent at the joint not shown in FIG. 29.
FIG. 30 through FIG. 32 show conventional joint structures between the first and the second substrate splits. According to the joint structure shown in FIG. 30, a first substrate split 111 and a second substrate split 121 are joined together via a plurality of lead wires R. Each of the lead wires R is bonded to wiring patterns P111, P121 provided on respective surfaces of the substrate splits 111, 121. The lead wires R can be bent easily. The substrate splits 111, 121 are electrically interconnected via the lead wires R. The circuit substrate thus provided by the substrate splits 111, 121 and joined by the above joint structure includes a connector C, electronic parts D and so on, yet the circuit substrate can be incorporated into the case 1 through effective use of an internal space not occupied by the batteries 2.
According to the joint structure shown in FIG. 31, a first and a second substrate splits 112, 122 are joined together via an intermediate member 200. The substrate splits 112, 122 are each provided by a multi-layer substrate having through holes (not illustrated). When making this joint structure, first, the intermediate member 200 is made from a flexible film material 200a by forming thereon with a conductive pattern 200b. Then, after various steps of manufacture, finally, two ends of the intermediate member 200 are sandwiched by respective pairs of rigid members 112a, 112b, 122a, 122b, to obtain the circuit substrate as shown in FIG. 31. Thus, according to the circuit substrate in FIG. 31, the intermediate member 200 is exposed at the joint. The circuit substrate can be easily bent at this exposed portion. Therefore, the joint structure according to Conventional Example 2 offers the same advantage as achieved by the previous Conventional Example 1.
Further, according to a joint structure shown in FIG. 32, the circuit substrate can be made through manufacturing steps simpler than those for the conventional examples shown in FIG. 30 and FIG. 31. Specifically, a first and a second substrate splits 113, 123 are joined together and electrically interconnected with each other, simply via metal strips 300, 310. The circuit substrate can be bent into a desired shape by bending the metal strips 300, 310.
Now, the circuit substrate with any of the above conventional joint structures has a problem to be described below. Specifically, in the circuit substrate with the joint structure shown in FIG. 30, the lead wires R that serve as joint parts are short and very fine, which makes it difficult to handle by a manufacturing machine. Therefore, according to this circuit substrate, the lead wires R can be attached to the connecting region only by manual operation. With this circuit substrate, it is difficult to improve productivity through factory automation for example.
According to the joint structure shown in FIG. 31, it is anticipated that manufacturing process can be automated. However, this joint structure is complex in that the circuit substrate that includes the substrate splits 112, 122 and the intermediate member 200 has a multi-layer structure. Therefore, this circuit substrate requires a large number of manufacturing steps, leading to increase in the cost of circuit substrate itself.
According to the joint structure shown in FIG. 32, it is possible to bend the metal strips 300, 310. However, this joint structure does not allow the joint to be flexibly bent as the circuit substrate is being shaped for appropriate fitting into the case 1 of the battery pack P. Therefore, with this joint structure, operation of incorporating the circuit substrate cannot be efficient, requiring a laborious procedure. Furthermore, the joint structure offers no such protection to the metal strips 300, 310 as electrical insulation and resistance to heat, posing another problem of low reliability in electrical continuity.
An object of the present invention is to provide a circuit substrate capable of eliminating or at least reducing the problems described above.
Another object of the present invention is to provide a battery pack incorporating such a circuit substrate.
Another object of the present invention is to provide a method of manufacturing such a circuit substrate.
A circuit substrate provided by a first aspect of the present invention comprises:
a first substrate split formed with a predetermined wiring pattern and a second substrate split formed with a predetermined wiring pattern. The substrate splits are electrically and/or mechanically joined together, and the circuit substrate is bendable at the joint.
The joint is provided by a bendable joint member including a plurality of leads disposed in parallel and held by a thin piece of base film integrally therewith. The joint member is attached to the first and the second substrate splits.
According to a preferred embodiment of the present invention, the first and the second substrate splits are electrically interconnected via the leads.
Preferably, the first and the second substrate splits are rigid printed wiring substrates.
According to the above arrangement, the joint member is provided by a plurality of leads held by the base film integrally therewith. The joint member is provided with electrical insulation, heat resistance and so on by the base film. Therefore, the joint member serves as a reliable electrical conductor. Further, the joint member is provided with a certain level of stiffness by the leads. The joint member is attached as the joint at a joint portion between the first and the second substrate splits. Therefore, the joint member can be handled easily by automated machinery, making possible to improve productivity through automation.
Further, the first and the second substrate splits can be provided by a simple substrate having one or two surfaces each formed with a wiring pattern. The joint member can be manufactured separately from the substrate splits, and then attached to the substrate splits. Therefore, each step of manufacturing the first and the second substrate splits as well as steps of manufacturing the joint member can be simple. Further, the joint member enables to reduce the number of parts and materials necessary for the circuit substrate as a whole, and to reduce product cost of the circuit substrate as a whole. Further, the joint member has a certain level of stiffness provided by the leads. The joint member is flexibly bendable because of the thin piece of base film. Therefore, the circuit substrate can be efficiently fitted into e.g. a case while being bent flexibly at the joint provided by the joint member.
According to a preferred embodiment of the present invention, the leads are shaped in a gull wing pattern. The attachment of the joint member is provided by each of the leads having its two ends connected to predetermined places respectively of the substrate splits.
With the above arrangement, the joint member as a whole is shaped into the gull wing pattern along the length of the leads, into a shape similar to a packaged semiconductor chip. Therefore, according to the above arrangement, the joint member can be reliably bonded at its connecting points, by using an automatic machine such as a chip mounter. Also, according to the above arrangement, it is easy to automate the connecting operation while maintaining reliability in the electrical connection.
According to a preferred embodiment of the present invention, the leads in mutual adjacency are separated from each other at a predetermined interval by a retainer formed between the leads.
With the above arrangement, the leads disposed in parallel to each other are sandwiched by films from above and below. Under the sandwiched state, mutually adjacent leads are retained at a predetermined distance from each other by the retainer formed between the leads. Therefore, according to the above arrangement, it becomes possible to electrically insulate the mutually adjacent leads from each other. Further it becomes possible to prevent the leads from short-circuiting, and to keep a reliable circuit operation.
Preferably, the base film includes a tape layer and an adhesive bonding layer formed on a lower surface of the tape layer.
The bonding layer is thermally melted to fill space between the leads and then is set, thereby formed as the retainer.
With the above arrangement, when the leads are sandwiched between the films, since the film is formed with a thermo-melting bonding layer, even if the gap between the leads is very small, it is possible to fill the gap with the bonding layer, without leaving air gap between the leads. Therefore, the films can be favorably pasted to each of the leads via the bonding layer. The bonding layer enables to retain the leads firmly in mutual adjacency. The bonding layer is preferably provided by e.g. a silicone adhesive or an epoxy adhesive.
According to a preferred embodiment of the present invention, the lead has its end portions, except end faces, soldered to terminals of the substrate splits.
With the above arrangement, when the substrate splits are interconnected by the joint member, the bonding is provided by the end portions of the leads, except the end faces, of the joint member which are fixed by the solder thereby connected to corresponding terminal portions of the substrate splits. For example, if the joint member is part of a tie bar during the manufacture, the lead is finally cut off the tie bar when the tie bar becomes unnecessary. If the soldering is performed while the cut faces are left exposed, solder fillet is not formed favorably. However, if the soldering is performed to the end portion except the end faces, i.e. the cut faces, solder fillet is formed appropriately along side surfaces of the lead. The above arrangement enables favorable and firm bonding between the lead and the terminal portions of the substrate splits.
Preferably, the lead has end portions bent, with the end faces oriented generally upward.
With the above arrangement, in order to solder the end portion of the lead except the end face, to the terminal portion of the substrate split, the end portion of the lead should simply be bent to turn the end face generally upward.
Preferably, the lead is formed with a portion narrower than the other portion of the lead, for bending.
With the above arrangement, the formation of the narrow portion in the lead reduces stress when the lead is bent in a pressing process, and therefore the lead can bend easily. Thus, it becomes possible to reduce such a problem as caused during the solder re-flow operation, that the angle of bending is increased due to softening of the base film. It also becomes possible to prevent such a problem that the ends of the leads are leveraged up and outward for example, as viewed in a transversal sectional view. Therefore, the end portions of the lead are appropriately soldered to respective terminals of the substrate splits.
According to a preferred embodiment of the present invention, the first and/or the second substrate splits are joined with still another substrate split via another of the joint member.
The above arrangement enables to manufacture a circuit substrate of a construction in which a large number of the substrate splits are collectively jointed via a plurality of the joint members. Further, each of the joints offers flexible bending via the joint member. As a result, according to this arrangement, even if the circuit substrate is large as a whole, accommodating space within the case can be effectively used by bending the circuit substrate into a desired shape.
A circuit substrate provided by a second aspect of the present invention comprises:
a first substrate split formed with a predetermined wiring pattern and a second substrate split formed with a predetermined wiring pattern joined with each other electrically and/or mechanically by a bendable joint member.
The joint member includes:
a first jointer connecting the substrate splits on their respective upper surfaces, and
a second jointer connecting the substrate splits on their respective lower surfaces.
With the above arrangement, the jointers for joining the substrate splits are disposed in such a way that one of the jointers connects respective upper surfaces of the substrate splits, whereas the other jointer connects respective lower surfaces. Therefore, according to this arrangement, a substantially large number of wirings can be provided in the entire joint member, enabling to increase electric current capacity in the joint member as a whole. According to this arrangement, even if a relatively high amperage of power voltage signal is passed in the signal transmission between the substrate splits, there is no need for increasing the size of the joint member itself. Still further, the arrangement allows favorable transmission of electric signals without need for increasing the number of wirings per joint member.
Preferably, the first jointer is longer than the second jointer.
With the above arrangement, if the circuit substrate as a whole is bent for example, the first and the second jointers are bent. With the arrangement that the first jointer is longer than the second jointer, the first jointer can be bent reasonably naturally, enfolding the second jointer from outside.
Preferably, the first jointer has an intermediate portion bent to be spaced from the second jointer by a predetermined distance.
With this arrangement, since the first jointer has its intermediate portion bent, it is possible to provide an effective space inward of the first jointer when the two joint members are bent. Therefore, according to the above arrangement, the distance between the two joint members can be kept more reliably, enabling to prevent the joint members from contacting each other.
Preferably, at least the first jointer includes a plurality of leads disposed in parallel to each other and films sandwiching the leads from above and below.
According to the above arrangement, the joint member has a structure in which each of the leads is held by the films integrally therewith. Therefore, according to this arrangement, like the embodiments described earlier, the joint member can be formed into a shape similar to a common, flat package of semiconductor chip. Thus, the joint member can be reliably bonded to the substrate splits by using an automatic machine such as a suction collet.
Preferably, at least the second jointer includes a plurality of connecting strips disposed in parallel to each other.
With the above arrangement, the second jointer can be given a simpler construction than such a jointer in which a plurality of leads are sandwiched between the films. Thus, it becomes possible to reduce parts cost and manufacturing cost.
Preferably, each of the joint members is dedicated to a specific kind of electric signal. Specifically, one of the joint members carries a power voltage signal and the other of the joint members carries a control signal that differs from the power voltage signal. Here, the term xe2x80x9ccontrol signalxe2x80x9d refers collectively to signals transmittable through the leads, such as data signal and control signal, other than the power voltage signal.
With the above arrangement, different kinds of electric signals, i.e. the power voltage signal and the control signal are transmitted in dedicated joint members respectively. Therefore, according to this arrangement, the path for the control signal is provided separately from the other joint member that serves as the path for the power voltage signal. As a result, it becomes possible to greatly reduce adverse influence of noise for example, from the power voltage signal to the control signal.
A third aspect of the present invention provides a battery pack.
The battery pack comprises: a circuit substrate comprising a first substrate split formed with a predetermined wiring pattern and a second substrate split formed with a predetermined wiring pattern. The substrate splits are electrically and/or mechanically joined together. The circuit substrate is bendable at the joint, connected with a battery, and incorporated in a case.
The joint is provided by a bendable joint member including a plurality of leads disposed in parallel and held by a thin piece of base film integrally therewith. The joint member is attached to the first and the second substrate splits.
The circuit substrate incorporated in the case is bent to yield to the battery.
With the above arrangement, the circuit substrate incorporated in the case is the one according to the above first aspect. Therefore, according to this arrangement, the above described advantages offered by the first aspect are instantly obtained. Further, the circuit substrate is incorporated as bent to yield the battery, making possible to dispose the circuit substrate favorably within the case, leading to an advantage of a favorably reduced outer dimension of the battery pack.
A fourth aspect of the present invention provides a method of manufacturing a circuit substrate comprising a first substrate split formed with a predetermined wiring pattern and a second substrate split formed with a predetermined wiring pattern. The substrate splits are electrically and/or mechanically joined together, and the circuit substrate is bendable at the joint. The method comprises:
a step of manufacturing, as a member to attach as the joint, a bendable joint member including a plurality of leads disposed in parallel and held by a thin piece of base film integrally therewith; and
a step of attaching the joint member as the joint, by first placing the first and the second substrate splits closely to each other generally on a same plane, and then connecting end portions of each lead to predetermined adjacent places respectively of the substrate splits.
The above method of manufacturing the circuit substrate enables to realize the advantages offered by the circuit substrate according to the first aspect in actual manufacturing steps. As a result, according to the present method of manufacture, a structurally superior circuit substrate can be obtained.
Preferably, the leads are first held by the base film integrally therewith, and then deformed into a gull wing pattern, in the step of manufacturing the joint member.
Further, the ends of each lead are aligned with the respective predetermined places of the substrate splits for the connection, in the step of attaching the joint member.
According to the above method of manufacturing the circuit substrate, the joint member is entirely shaped into a gull wing pattern along the leads. According to the present method, the joint member can be handled by such a machine as a chip mounter. The electrical connection between the first and the second substrate splits are reliably established by the joint member.
Preferably, the step of manufacturing the joint member includes: preparing an electrically conductive frame formed with a pattern of slit group continually in a longitudinal direction, (The slit pattern is formed in a crosswise direction and to serve as the plurality of leads); pasting tapes that are to serve as the base film, perpendicularly to and integrally with the slit groups; and then cutting the conductive frame into pieces each including the slit group, thereby obtaining a plurality of joint members.
According to the above method of manufacture, the conductive frame which is to be the leads is integrated with films in the form of tape which is to be the base film. Then, the joint members can be obtained by continually or simultaneously cutting the integrated component at predetermined places. According to the present method, in such a step of manufacturing a part as the above, a plurality of the joint members can be efficiently and automatically produced.
According to a preferred embodiment of the present invention, the step of manufacturing the joint member includes: sandwiching the leads that are disposed in parallel to each other, from above and below, between films extending perpendicularly to the leads; applying heat thereby allowing a bonding layer of each film to melt to fill spaces between the leads; allowing solidification at a room temperature, thereby forming from the bending layer a retainer for retaining each lead in separation from adjacent ones at a predetermined distance.
According to the above method of manufacture, by sandwiching the leads disposed in parallel to each other, with the films from above and below, and applying heat, the bonding layers of the films are melted to fill space between the leads. Then, by solidifying the bonding layer at a room temperature, the retainer capable of retaining mutually adjacent leads at a predetermined distance can be formed. As described, the retainer that retains the mutually adjacent leads can be formed by a simple method such as applying heat when the tapes are attached to the leads.
According to a preferred embodiment of the present invention, the step of manufacturing the joint member includes: forming a recess having a generally V-shaped section at each end portion of the lead; bending a portion of the lead which is inward of each recess; connecting each bent portion to a terminal in corresponding one of the substrate splits; and thereafter cutting the lead at the recess.
According to the above method of manufacture, the lead is formed with a generally V-shaped recess, then the end portions of the lead are connected to the terminal portions of the respective substrate splits, and finally the lead is cut at the recess. For example, if the joint member is part of a tie bar during the manufacture, the lead is cut off the tie bar finally, when the tie bar becomes unnecessary. Thus, according to the present method of manufacture, since the tie bar is removed after the joint member has been connected to the substrate splits, it becomes possible to reduce inconsistency otherwise results if the cutting of the leads is made before the joint member has been connected to the substrate splits.
Further, a portion of the lead which is inward of each recess is bent, and the bent portion is connected to the terminal of the substrate split. Therefore, end portion of the lead except the cut face (end face) is connected to the terminal portion, allowing solder fillet to form appropriately, enabling to bond the lead firmly to the terminal portion of the substrate split.
A fifth aspect of the present invention provides a method of manufacturing a circuit substrate. The method comprises: a step of making substrate splits; a step of making a bendable joint member electrically and/or mechanically joining the substrate splits together; and a step of joining the substrate splits with the joint member.
A first jointer is made in the step of making the joint member, by first sandwiching leads disposed in parallel to each other, from above and below, with films extending perpendicularly to the leads, and then bending the leads at their intermediate portion.
A second jointer is provided by a plurality of connecting strips disposed in parallel to each other.
In the step of joining the substrate splits with the joint member, the substrate splits are joined together by the first jointer connecting respective upper surfaces of the substrate splits.
Further, the substrate splits are joined together by the second jointer connecting respective lower surfaces of the substrate splits.
Other features and advantages of the present invention will become clearer from the following description of embodiments to be presented with reference to the accompanying drawings.